It was a beautiful night's sky, clear and full of stars. I was looking out of the window towards the East. I was gazing up at the moon, the stars and at the large star, Sirius (I believe that's what it's called); it was twinkling, as usual. Then from the corner of my eye I saw a huge "star" that was once still, suddenly dart off, going Southeast. It was much larger than the other stars. It moved at an incredible speed. It was bright white and circular in shape. Familar with planes flying over, it clearly had no blinking red and/or white likes, like planes. And usually, at night, you can barely see the plane, except for it's blinking lights, whereas this was completely covered in white light and was very bright. As it increased in speed, it moved across the sky in a horizontal direction, then it began moving upward on an angle, going higher and higher. Then all of a sudden it disappeared.